In the first decade of our century, carbon nanotubes (CNTs) became a wonderful emitting material for field-emission (FE) of electrons. The carbon nanotube field-emission (CNT-FE) cathodes showed the possibility of low threshold voltage, therefore low power operation, together with a long lifetime, high brightness, and coherent beams of electrons. Thanks to this, CNT-FE cathodes have come ahead of increasing demand for novel self-sustaining and miniaturized devices performing as X-ray tubes, X-ray spectrometers, and electron microscopes, which possess low weight and might work without the need of the specialized equipped room, e.g., in a harsh environment and inaccessible-so-far areas. In this review, the author discusses the current state of CNT-FE cathode research using CNT suspensions. Included in this review are the basics of cathode operation, an evaluation, and fabrication techniques. The cathodes are compared based on performance and correlated issues. The author includes the advancement in field-emission enhancement by postprocess treatments, incorporation of fillers, and the use of film coatings with lower work functions than that of CNTs. Each approach is discussed in the context of the CNT-FE cathode operating factors. Finally, we discuss the issues and perspectives of the CNT-FE cathode research and development.

Flexible, screen-printed electrode systems offer significant advantages in biomedical applications due to their rapid fabrication capability and adaptability to irregular surfaces. Despite this, no flexible, screen-printed biosensors for pH measurement are readily available on the market. This paper introduces an innovative fabrication technique for integrating flexible screen-printed electrode (SPE) systems with multi-wall carbon nanotubes (MWCNTs). These SPE systems feature flexible screen-printed working electrodes functionalized with f-MWCNT for pH sensing, achieving a fabrication success rate of 78.57%. Furthermore, these SPE systems have been optimized to improve voltage changes and thoroughly characterized for performance using pH buffer solutions. This was done utilizing open-circuit potentiometry. The results demonstrate that the SPE systems can detect pH ranges from 4.0 to 8.9 with an average sensitivity of 33.66 mV/pH, an output range of 202.62 mV, a settling time of 19.71 s, and stability for up to 72 hours. Additionally, the SPE systems have been tested with artificial saliva within the pH range of 5.0 to 8.3, achieving a sensitivity of 44.86 mV/pH and an output range of 192.90 mV. These findings pave the way for further exploration in pH sensing research, particularly utilizing SPE systems coated with MWCNTs.

In order to establish design rules for micro-supercapacitors (micro-SCs), the influence of electrode shape, specifically aspect ratio, was investigated on the operational speed of micro-SCs. The operational speed, as characterized by the relaxation time constant, was found to nonlinearly decrease (85 to ∼0.5 ms) as the electrode aspect ratio increased (0.2 to 7). This was achieved by simplifying the electrode design to a basic parallel electrode geometry. In so doing, all factors, such as electrode height, volume, electrolyte volume, inter-electrode separation, etc. could be maintained while adjusting the electrode aspect ratio (AR). In addition, the results showed that the relaxation time constant showed only moderate improvement for aspect ratios above 1, illustrating the limitation on this single shape parameter. Investigation into the underlying reasons for this behavior showed that the observed dependence of the relaxation time constant with the electrode AR originated from differences in the electrolyte resistance within the electrode for each electrode shape as determined by electrochemical impedance spectroscopy. Although these results demonstrate that the operational speed of a micro-SC can be improved by increasing the electrode AR, our results also show that this factor alone is insufficient to improve the speed into the microsecond regime within our experimental scope.

This paper focuses on electron emitters formed using seamless hybrid shaping of the ceramic 3D‐printed cone (as a supporting structure) and a conductive emitting film obtained from the suspension of dispersed carbon nanotubes (CNT). The ceramic cone is post‐process fired to achieve a pure ceramic cone that is coated with emitting CNT mesh film. Meanwhile, a cone‐based polymer emitter is evaluated. The resulting emitter exhibits non‐linear current‐voltage characteristics reaching maximum 0.6 mA anode current with a turn‐on‐field voltage below 1 Vµm⁻¹ and minimal current fluctuation over time. Additionally, the ceramic emitter arrays fabricated using the same technique are demonstrated: if the tip angle and shape in a microscale have tunability in emission is confirmed, meanwhile, the type of volatile gases released during the emission is confirmed using a residual gas analyzer (RGA). The motivation and challenge are to use 3D printing to enable freedom in designing and forming the emitter tip shape and angle and to present the perspective and challenges to use the 3D printing technique combined with the seamless shaping for the CNT mesh film to tune the emitter performance. Especially as this technique and 3D‐printed materials have not been previously employed for electron emitters.

In this article, a near infrared (NIR)‐responsive microscale cantilever made of the novel 3D printable composite based on the ceramic sepiolite and graphene flakes is presented. The developed composite benefits from no necessity to use complex and high‐energy processes and absorbs NIR light and followed by mechanical work, which results in shape transformations of the cantilever. With the irradiation of 1064 nm wavelength, the composite cantilever exhibits the displacement of average—1.3 ± 0.18 mm—with the fast photothermal responsiveness as the laser beam is ON–OFF within 1.7 s. The displacement measurements is based on the video recording using a monochrome camera. Additional to the actuation performance, the material characteristics are presented for the composite and its ingredients including the scanning electron microscope energy dispersive using X­ray analysis, Brunauer–Emmett–Teller, thermogravimetric analysis, and Fourier transform infrared spectroscopy analysis confirming that the addition of the graphene flakes and the ceramic particles to the resin does not change functional groups.